The present invention relates to storage system technology.
Storage systems of a type connected directly to a network, termed NAS (Network Attached Storage) are in widespread use. The use of such a storage system allows a filesystem to be shared among clients via the network, and enables the same file to be accessed by clients.
In recent years, there have been attempts to realize effective data utilization and efficient storage investment by storing data on storage media of optimal cost, depending on value of the data based on its importance or other consideration. This approach is termed information lifecycle management (ILM). For example, data of relatively high value is stored on an expensive FC (Fibre Channel) compatible hard disk, while data of relatively low value is stored on an inexpensive ATA compatible hard disk. Note that, FC compatible hard disks are characterized by higher reliability and faster access time than ATA compatible hard disks.
Where ILM is implemented using a plurality of types of storage media, such as an FC compatible hard disk and an ATA compatible hard disk, typical practice is to establish a logical unit for each type of storage medium, and to build a filesystem for, each logical unit. That is, when implementing ILM, a plurality of filesystems are built for each type of storage medium.
Employing existing technology, it is also possible to establish one logical unit for the plurality of types of storage media, and to build one filesystem on the logical unit. However, in this case, it becomes difficult to deploy ILM appropriately, that is, to utilize the plurality of types of storage media in an efficient manner.